1. Field of the Invention
The present invention relates to a pushbutton operated multiple switch assembly by which only one of a plurality of switches arranged on a printed circuit board can be activated.
2. Prior Art
FIGS. 5A, 5B and 5C are cross sections showing one example of a conventional pushbutton mechanism. In the figures, reference numeral I represents a pushbutton whose cross section is shaped like a letter U upside down. Designated 2a, 2b, 2c and 2d are first to fourth switch activating portions located on the peripheral portion of and formed integral with the pushbutton I. These switch activating portions form a part of the printed circuit board. Denoted 3a, 3b, 3c and 3d are first to fourth switches located at the centers of the sides of a quadrangle on a printed circuit board 4. Numeral 5 is a decorative surface panel. A cushion 6 is installed between the printed circuit board 4 and the pushbutton 1 to support the pushbutton 1.
Now, the operation of the above pushbutton mechanism will be described. When a point on the pushbutton 1 above the first switch 3a is depressed, the pushbutton 1 is inclined compressing the cushion 6, causing the first switch activating portion 2a to move down to energize the first switch 3a. Next, when the pushbutton 1 is released, it returns to its original position by the recovering force of the cushion 6, resetting the switch 3a. The second to fourth switches 3b, 3c, 3d also perform the same operation.
The conventional pushbutton mechanism of the above construction has the following drawback. When a point on the pushbutton 1 between the first and second switches 3a, 3b is pushed, both the first switch activating portion 2a and the second switch activating portion 2b move down turning on the first and second switches 3a, 3b simultaneously. This could happen for other combinations of second and third switches 3b, 3c, of third and fourth switches 3c, 3d, and of fourth and first switches 3d, 3a. When the pushbutton 1 is pressed at an intermediate point of the four switches 3a, 3b, 3c, 3d, the entire pushbutton 1 moves down causing all four switch activating portions 2a, 2b, 2c, 2d to turn on all the four switches 3a, 3b, 3c, 3d at one time. To avoid activating two or more switches 3a, 3b, 3c, 3d simultaneously requires an operator to use caution in selecting and pressing the correct position on the pushbutton 1.